E. coli ribosomal protein S1, essential for the initiation of protein synthesis, will be investigated with respect to the functional implications of its binding at the 3' end of 16s rRNA. The binding sites of puromycin and tRNA to E. coli rRNA will be examined by isolation and RNA fingerprint analysis of specific RNA fragments on to which puromycin and tRNA have been photoincorporated. The biosynthesis of E. coli ribosomes will be investigated using strains deficient in RNases involved in processing precursor rRNAs. The protein and RNA composition of precursor particles will be characterized. The structure of the yeast ribosome will be studied by the isolation of specific fragments cleaved from the ribosome by RNase treatment and subsequent characterization of their protein and RNA composition.